Former President Barack Obama said he did not see evidence that aliens “have made contact with us,” after sending social media abuzz by saying aliens were real on a podcast over the weekend.

For decades, scientists have searched the skies for signs of extraterrestrial technology. A study from EPFL asks a sharp question: if alien signals have already reached Earth without us noticing, what should we realistically expect to detect today?

Planet K2-18b, an apparent water world 124 light years away, has been seen as a promising location in the search for aliens, but telescopes on Earth failed to pick up any radio transmissions